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Old 11-16-2009, 11:40 AM
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Ported vacuum switch question

Hello guys,
It is SBC 305 in 78 Monte Carlo, everything stock.
I have two ported vacuum switches, very similar to the one on the picture. One on the manifold, the other one on thermostat housing. I need to change the one on the manifold.
I see there are three different types, blue, green and purple.
What type should I use? Are the two switches the same?

Thanks for the help,
Ivo
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Old 11-16-2009, 05:21 PM
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All these are is really emission devices I would remove and not bother to replace. They are designed to give the devices vacuum when the engine gets up to temp. Find what they control if it`s emission devices such as the dreaded exhaust flap on the passengers side exhaust pipe I would bypass it. If another operates the EGR I would bypass that too.
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Old 11-18-2009, 10:54 AM
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Hi DoubleVision,

You are absolutely correct. One of them, the broken one actually, controls the EGR valve and something on the evaporator canister, the other one controls "dreaded exhaust flap".

What do you mean by "bypass"? To connect the vacuum source directly to the device, EGR etc. ? Or not to use it at all, EGR etc?

Anyway, do both valves the same and interchangeable? My ones are black.

I am still on my way to reduce fuel consumption , thank you for helping me on my previous tread

Regards,
Ivo
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Old 11-18-2009, 11:29 AM
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Yep I mean bypass as in not use. Simply plug the vacuum source, I would however, keep the evap system operational. I don`t know what system yours uses but what I`ve seen in the past is a PCV valve with dual fittings, one to the carb and the other to the evap canister. It should be easy to adapt yours to this set up. Some 3/8 vacuum hose and a 2 way PCV valve.
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